Thyroid issues may be an issue. I do recommend seeing a doctor.
When I had my thyroid removed, I don't know if it was the thyroid or the chemo, but that's when my hair turned wavy. I had stick straight hair as a child.
Averages out at 2b, ranges from 1c to 3a, very fine
Mane 'n Tail co-wash + leave-in
Clarifying shampoo every few weeks